The innovative PRE-SAFE system first tensions the seatbelts if the car senses an impending collision.  (The system uses resettable electric tensioners in addition to the existing pyrotechnic belt tensioners).

What’s more, if the front passenger seat is overly reclined or forward, PRE-SAFE moves it to a more favorable crash position.  If the seat cushion angle of the front passenger seat is too shallow, it is also re-adjusted to help prevent submarining.

Finally, if the vehicle skids (sometimes a precursor to rollover), the system can automatically close the sunroof and side windows.  If a crash is averted, the electric belt tensioners automatically relax and are ready to deploy again.


If necessary, PRE-SAFE reacts to fishtailing (or oversteer) as well as “plowing” (or understeer) by using existing sensors for ESP stability control to measure steering angle, vehicle yaw and lateral acceleration.  Emergency braking can also trigger PRE-SAFE, which monitors sensors for the Brake Assist system as well. The development of PRE-SAFE was based on the findings of Mercedes-Benz accident researchers, who concluded that about two-thirds of all accidents are preceded by driving events that indicate the possibility of an impending crash, such as skidding, emergency braking or a sudden evasive maneuver – all of which can provide valuable seconds of advance warning before impact.